Leaders of the Group of Seven rich nations are set to clash with a combative U.S. President Donald Trump on Friday when they pressure him to lift sanctions on steel and aluminum they fear could lead to a trade war.

Leaders of the Group of Seven rich nations are set to clash with a combative U.S. President Donald Trump on Friday when they pressure him to lift sanctions on steel and aluminum they fear could lead to a trade war.

The confrontation threatens to rupture a body that during its 43-year history has traditionally sought to find consensus on the economy and other issues.

Trump, who aides say has little interest in multilateralism, twice attacked Canadian Prime Minister Justin Trudeau on Twitter on Thursday and officials concede the mood is likely to be exceptionally tense.

"There will be some serious disagreements on a lot of things," a Canadian official told reporters late on Thursday.

Although Trump says the tariffs are necessary to protect U.S. industry, Canada and the European Union have denounced them as illegal and are preparing retaliatory measures.

French President Emmanuel Macron said on Thursday leaders needed to be civil at the summit but he is clearly losing patience with the U.S. President, suggesting the other six members of the G7 could form their own grouping if necessary.

British Prime Minister Theresa May took a more measured tone, telling reporters she wanted the European Union to use restraint in its retaliation to the U.S. tariffs and that the response must be proportionate and legal.

Trump showed no sign of backing down on Thursday, first taking to Twitter to accuse both France and Canada of imposing massive tariffs on U.S. goods and then accusing Trudeau of "being so indignant."

In response, the Canadian official replied that "the prime minister and the president have very frank, direct, candid, honest conversations." Trudeau and Trump are due to meet on Friday "and they will have lots to talk about," the official added.

The White House subsequently announced the president would be leaving on Saturday, before the summit formally ends, to fly to Singapore for a meeting with North Korean leader Kim Jong Un.

While the G7 leaders have largely praised Trump for his efforts to stabilize the Korean peninsula, they are unhappy he pulled out of an agreement designed to limit Iran's nuclear ambitions.

The arguments threaten to derail a meeting that Trudeau had planned to focus on inclusive growth, gender equality and protecting oceans.

The Canadian official said Trudeau remained optimistic that the summit could help find common solutions to issues such as growth and environmental protection.